A gas laser generator comprising parallel superimposed flat plates is known comprising: firstly, a first metallic plate, a first insulating plate and a second metallic plate forming together a first excitation line and secondly, a third metallic plate, a second insulating plate and a fourth metallic plate forming a second excitation line. The first and second metallic plates are spaced apart from each other and each includes a slot separating it into two distinct parts, these slots being disposed facing each other. Two electrodes are disposed on either side of these slots and are connected to the second and third metallic plates along an edge of these slots. A laser tube surrounding the electrodes and containing an active gaseous medium is disposed in the space situated between the second and third metallic plates along these slots. Lastly, this gas laser generator comprises a spark gap suitable for setting up a brief electric discharge generating in the two excitation lines simultaneously a travelling current wave.
In the gas laser described hereinabove, a triangular shape is preferably given to the metallic plates. The spark gap occupies an apex of the triangle and the laser tube occupies the opposite side to this apex. The dimensions of the side of the triangle are so determined that the difference in time between the instant of arrival of the wave at the respective ends of the tube corresponds to the time taken by the laser light radiation to go from one end to the other of this tube.
But, because of its circular form, the current wave excites the active gas at a speed which cannot be equal at all times to the propagation speed of the laser radiation in the tube. Disadvantages and more particularly a reduction in the power of the laser result therefrom.
It is known that it is possible, by cutting out metallic plates in the shape of a parabola and by placing the spark gap at the focus of these parabolas, to set up a rectilinear travelling current wave, which in principle makes it possible to remedy these drawbacks. But, in the case of a laser comprising two excitation lines, it is then necessary to provide a spark gap on each line, this causing other disadvantages, for it is difficult to synchronise the discharges of two spark gaps.
Prefered embodiments of the present invention remedy these disadvantages and produce a gas laser generator comprising two flat-plate excitation lines, in which the arrival of the current wave along the laser tube is effected at speed which is equal at each instant to that of the laser radiation.